Filter structure for the removal of undesirable elements from a fluid or vapor has developed through the years to take advantage of newly developed materials and techniques. The introduction of non-woven webs as filter material subsequently led to the formation of pleated and corrugated structures from the non-woven materials in order to increase the surface area of the filter material exposed to the fluid, as well as decrease the pressure drop or resistance as the fluid passed through the material. Numerous techniques for the corrugation and use of corrugated non-woven webs have been developed as described, for example, in U.S. Pat. No. 5,753,343 (Braun et al.), including stacking of multiple layers of corrugated and non-corrugated material. In such previously developed examples, emphasis has typically been on increased surface area by using corrugations or channels formed from the filter material to pass straight across or through the ultimate filter.
Although improvements have been made to increase filter efficiency and decrease filter pressure drop or resistance, an ongoing need exists to still further provide improvements in these areas. Additionally, the development of new and different filter materials presents an ongoing challenge to utilize such materials effectively to produce efficient and cost effective filter applications. Further, improved adsorbent filters with increased efficiency at a desired pressure drop, or reduced pressure drop at a desired efficiency are also needed.